1. Field of the Invention
The invention relates to pipeline connectors and more particularly to means for sealingly connecting pipes which are axially misaligned.
2. Description of the Related Art
The use of pipelines for handling large volumes of fluids is widely known. High-volume pipelines are commonly used for fluid hydrocarbons such as oil. The pipelines used in these applications typically consist of a number of pipe sections which are connected end-to-end to form a single conduit. In many cases, adjoining pipe sections are axially aligned so that they can be connected by means of standard flanges at the respective ends of the pipes which are bolted together. In some cases, however, adjoining pipe sections may be misaligned so that a standard bolted-flange connection cannot form a seal or cannot be made at all. For example, in marine environments, it may not be possible to keep the pipe sections aligned when they are laid, and they may become misaligned due to environmental forces or repairs on the pipeline.
Various connectors have therefore been developed to allow pipe sections which are positioned at a slight angle with respect to each other to be sealingly connected. These connectors are sometimes referred to as misalignment flanges, ball connectors or swivel couplings. The structure of these swivel couplings generally comprises a ball member having a spherical, outwardly-facing surface, a socket or swivel member having a spherical, inwardly-facing surface and a set of flanges or other means for holding the ball and socket members together. A sealing ring or gasket is normally placed between the opposing spherical surfaces of the ball member and the socket member to ensure that a seal is formed between the members. The flanges are tightened to hold the members in sealing contact.
The ball member of a swivel coupling is joined to one pipe section (typically by welding) while the swivel member is joined to an adjoining pipe section. The spherical sealing surfaces of the ball and swivel members allow the connection, and the pipe sections, to swivel around the center of the members while maintaining the opposing positions of the surfaces. When the pipe sections are in their final positions, the flanges of the connector are tightened so that further movement of the connector members is prevented.
A variety of swivel coupling designs are disclosed in the prior art. For example, U.S. Pat. No. 4,840,410 to Welkey discloses a swivel coupling which has a socket member, a ball member and a flange. When the ball member is positioned in mating contact with the socket member, the flange is bolted to the socket member to hold the ball and socket together. Before the flange is bolted to the socket, however, the flange is loose and is may move quite a bit with respect to the ball member. The loose flange may make this swivel coupling difficult to handle and may even cause damage to the contact surfaces between the flange and ball member, causing the swivel coupling not to swivel as smoothly as if the surfaces were undamaged. The Welkey patent also discloses a swivel coupling in which both the ball member and socket member have integral flanges. The bolt holes through the flanges each have varying diameters so that the bolts inserted therethrough can swivel with the coupling. This design, however, requires machining of the multi-diameter bolt holes as well as spherical washers and seats.
U.S. Pat. No. 4,381,871 to Dopyera et al. shows another example of a swivel coupling in the prior art. This swivel coupling has a pair of flanges adjacent to a ball member as well as a conventional coupling flange. In this swivel coupling, the flanges adjacent to the ball member are bolted together so that the ball member is captive between them. These three parts form a swiveling assembly which is then bolted to the conventional coupling flange. While this swivel coupling does not have a loose retainer flange, it must be sealed both between the ball member and the flange at the leading edge of the ball member and between that flange and the conventional coupling flange. Because this coupling must be sealed at both places, it may be more likely to leak than a swivel coupling which has fewer components. The number of parts in this swivel coupling also makes it more complex and expensive to manufacture than a design having fewer parts.